Unloading device for air-compressors



. c. H. REEDER.

UNLOADING DEVICE FOR AIR COMPRESSORS. APPLICATION FILED FEB. 13, 1920.

1,365,272, Patented Jan. 11, 1921.

ELECTRIC MOTOR CHARLES H. REEDER, OF ST. LOUIS, MISSOURI.

PATENT OFFICE.-

\l UNLOADIN'G DEVICE FOR AIR-COMPRESSORS.

Specification of Letters Patent.

Patented Jan. 11, 1921.

Application filed February 13, 1920. serial No. ssaasef To all whom it may concern:

Be it known that I, CHARLES H. REEDER, a citizen of the United States of America, and a resident of the city of St. Louis and State of Missouri, have invented certain new and useful Improvements in Unloading Devices for Air-Compressors, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

This invention relates to improvements in unloading devices for air compressors and the like. An object of the invention is to produce a simple and inexpensive automatic means whereby a motor driven compressor is permitted to run idly when the motor is started, and thereafter permitted to begin its effective operation when the motor is running at a comparatively high speed. This enables the motor to run freely durin' the starting period, and to pick up the loa while it is running at a predetermined operating speed.

Briefly stated, the device I have shown to illustrate one form of the invention, comprises a relief valve, or unloading valve, adapted to open and close the compression chamber of the compressor, electrically actuated means controlling said relief valve to retain the latter in its open position during the starting period, and a speed responsive switch controlling the electrical means, to permit closing of the relief valve when the compressor is driven at a predetermined operating speed. 0

The drawing is a diagrammatical view illustrating a motor driven compressor provided with an unloading device embodying the features of this invention.

An electric motor 1 is provided with an armature shaft 2 whereby a crank 3 is driven. The crank may be directly connected to the motor, as shown in the drawing, or any other suitable means may be employed to transmit motion to the crank. The compressor a piston 5, and a connecting rod 6 whereby the piston is connected to the crank 3. I

' 7 designates a relief valve, or unloading valve, which may be considered as the inlet valve of the compressor. This valve is adapted to open and close a port 8 so as to control communication between the compression chamber and the atmosphere. I do not may include a cylinder 4. containing deem it necessary to show the discharge valve nor the operating means therefor, these elements being old and well understood in the art to which my invention relates. A

When the motor is idle, and also during the start ng period, the valve 7 is held in the open position shown in the drawing, and the piston 5 can then move freely without compressing air in the cylinder. When the motor operates at a predetermined speed, the valve 7 is automatically released,.as hereafter pointed out, and permitted to close the port 8, so asto provide for compression of air in cylinder 4:.

9 designates a spring surrounding the stem of valve 7 and interposed between a valveguide 10 and a head 7 at the upper end of the valve stem. This spring 9 tends to cl e the relief valve 7.

The means for controlling the relief valve 7 preferably comprises an electro-magnet 12, which may be in the form of a solenoid having core 13 adapted to engage the head 7' at the upper end of the valve stem. When the solenoid is energized, its magnetic force will lift the core 13, thereby releasing the valve 7 and permitting the spring 9 to close said valve. gized, the core 13 will drop by gravity to open the valve 7, as shown in the drawing.1

If desired, the core 13 may be enlarged at its lower end to provide additional weight.

The means for energizing the solenoid in cludes a conductor 14: leading directly to the solenoid, and a conductor 15 provided with a switchconsisting of a movable spring contact member 16 and a fixed contact 17. When the apparatus is idle, the switch occupies the open position'shown in the sketch, and the solenoid core 13 then holds the valve 7 in itsopen position. When the ap-' paratu's is in operation, a speed responsive device acts upon movable contact 16 to retain it in engagement with contact 17, thereby closing the switch through which current flows to the solenoid.

The speed responsive elements ma be constructed in any suitable manner. 0 illustrate this feature I have shown a shaft section 18 extending from the crank 3 and provided with a wheel or housing 19 containing. a speed responsive device 'GODSlStlIlg of When the solenoid is deener-- weighted arms 20 pivoted at 21 to the housing and extending into an annular groove formed in a sleeve 22, the latter being slidsketch. This sleeve 22 has an annular flange 24 adapted to engage the movable switch member 16. As the speed increases, the

'weighted arms 20 will swing in response to centrifu al force, so as to move the sleeve 22, there y closing the switch 1617.

It will now be understood that-the relief valve 7 is held in its open position until the electric motor is operating at a predeterminedspeed, whereupon the switch 16--17 will be automatically closed, to complete the electric circuit whereby the solenoid is energized to release the valve 7, so there will be no substantial load on the motor until it is running'at a predetermined operating speed. The device herein disclosed will respond automatically to the operations of startingand stopping the motor. When the motor is idle, and, when it'is operating at low speeds, the automatic switch 1617 will be open and the solenoid core 13 will then retain the relief valve 7 in its open position, but when the motor is running at aspeed high enough to effectively drive the compressor, the speed responsive switch will be closed, so as to permit the transmission of electric current to the solenoid, whereby the core'13 is held in an inoperative position beyond the path of the head 7 at the upper end of the valve stem.

I claim: 7

1.. A motor driven compressor provided with a relief valve arranged to open and close'the compression chamber of the compressor, a valve opening device adapted to retain said relief valve in its open position,

an electro-magnet whereby said valve openin device is actuated to permit closing of said relief valve, a spring tending to close said relief valve, a switch controlling the transmission of current to said electro-magnet, and a speed responsive device whereby said switch is actuated, said speed responsive device being driven by the motor-so as to retain the switch in its closed position during normal operating speeds.

2. A motor driven compressor provided with a compression chamber having an opening through which fluid may be drawn into and discharged from the compressor, a pressure-relieving valve arranged to open and close said opening, a valve opening device adapted to retain said pressure-relieving sure-relieving valve when the motor and compressor are operated at a predetermined speed.

3. A motor driven compressor 4 provided with a relief valve adapted to open and close the compression chamber of the compressor, a valve opening device adapted to contact with said relief valve to retain it in its open position, a spring tending to close said valve, a magnet controlling said valve 'opening device whereby it is actuated to permit said spring to close the relief valve, a switch controlling transmission of current to said magnet, and a speed controlled device driven by the motor and operatively connected to said switch whereby said switch is retained in its closed position during normal, operative speeds of the motor but is permitted to open when the motor speed is below normal.

4. A motor driven compressor provided with a relief valve adapted to open and close the compression chamber of the compressorf spring means tending to close said relie valve, a weight tending to hold said relief valve in a normally openand inoperative position and adapted to overcome the closing tendency of said spring means, an electro-magnet controlling said weight and adapted to lift it to'permit the spring means to close said relief valve, a switch ,controlling said electromagnet, and a speed controlled device driven by the motor whereby said switch is actuated, said speed controlled device maintaining said switch closed at all speeds above normal speeds of the motorand permitting said switch to open below normal speed of the motor whereby the electro-magnet is energized during the normal operative speed of the motor and deenergized during lesser speeds.

In testimon that I claim the foregoing 

